The invention relates to a vehicle pneumatic tire having a sealing material on the interior side of the tire which, when the tire is damaged, at least approximately closes off a resulting leak, as well as to a warning system. With respect to the state of the art, reference is made, in addition to German published patent applications DE 10 2007 030 238 A1, DE 10 2007 008 043 A1 and DE 10 2009 006 707 A1, also to German patent document DE 10 2008 053 506 A1.
In the document mentioned second above, so-called electronic modules are known which have transponders and sensors by which, as a matter of priority, the pneumatic pressure in the tire is measured and is transmitted to a monitoring unit provided in the vehicle. Such tire modules, which in the present case, are called sensor units, are known to a person skilled in the art. Sensor units integrated in the wall of the tire are basically known; furthermore sensor units are known onto which a so-called foot made of a rubber material is formed, which is glued to the wall of the tire (German patent document DE 10 2007 030 238 A1), as well as sensor units which are inserted into a suitable holding device which is vulcanized or glued to the interior side of the tire, particularly to the interior side of its running surface (German patent document DE 10 2009 006 707 A1).
In the initially last-mentioned document, a so-called self-sealing tire is described which has a warning system. Self-sealing tires are distinguished by a sealing material applied at least to the interior side of the tire running surface, which sealing material, for example, in the event of a puncturing of the running surface caused by a nail or the like situated in an unfavorable position on the road, essentially tightly closes off the resulting hole. The tire according to this German patent document DE 10 2008 053 506 A1 also has a warning system which, when the tire is damaged, triggers a warning and which is formed by a network of electric lines which cover the sealing material.
Instead of such a high-expenditure warning system, a basically known tire pressure sensor unit could be arranged in a tire having a sealing material on the interior side of the tire, which sealing material, when the tire is damaged, at least approximately closes off a resulting leak. However, it was found that the gluing of such a compact sensor unit or its holding device onto the interior tire wall or interior side of the running surface, which has been common as a preferred joining technique, is not possible because simply no adhesive could be found that ensures a sufficient adhesion to such a sealing material.
It is to be indicated in the following how, nevertheless, a customary sensor unit for monitoring the pneumatic tire pressure at a pneumatic vehicle tire can be mounted on the interior side of the tire by means of a sealing material.
The achieving of this object is characterized in that the warning system constructed as a sensor unit known per se for monitoring the pneumatic pressure in the tire is fixed by way of an adhesive film to the interior side of the tire provided with the sealing material. The adhesive film is glued over a large surface onto the interior side of the tire. The surface of the adhesive film is several times larger than the base surface of the sensor unit or of a holding device for the sensor unit.
It was found that a significant enlargement of the surface of the sealing material included in an adhesive connection already represents a sufficient measure in order to be able to fasten a sensor unit for monitoring the pneumatic pressure in the tire securely by way of adhesion on an interior side of the tire or interior wall equipped or coated with this sealing material. This surface enlargement is achieved without any significant disadvantage with regard to the weight and, particularly, the imbalance by means of a so-called adhesive film, by which the tire pressure sensor unit can be fixed directly, or by way of a holding device indirectly, on the interior side of the tire. In this case, the adhesive film may cover the sensor unit, so that the sensor unit is situated between the adhesive film and the interior side of the tire, in which case, adhesive may additionally be provided between the sensor unit and the interior wall of the tire. In order to make it possible to then further faultlessly measure the pneumatic tire pressure when an essentially airtight adhesive film is used, it may be necessary to provide at least one hole or one duct at a suitable location in the adhesive film for a pressure compensation between the sensor unit and the tire interior. However, it is also contemplated to fasten, for example by gluing, the sensor unit to the side of the adhesive film that faces away of the interior wall of the tire, and/or, on the side of the adhesive film facing away from the interior wall of the tire, provide a holding device adapted to the sensor unit. In this case, the holding device may be formed into the adhesive film and is thereby quasi-formed by the adhesive film itself, or such a holding device assigned to the sensor unit may be connected with the adhesive film by means of gluing.
As mentioned above, by use of an adhesive film according to the invention, the surface of the sealing material included in the adhesive connection can be considerably enlarged; in other words, the surface of the adhesive film is several times larger, preferably larger by an order of magnitude of at least 10 to 20, than the base surface of the above-mentioned sensor unit facing the interior side of the tire or of the holding device for the sensor unit. For defining this ratio of sizes, the holding device is only a component provided for this holding function or, if the holding device is formed into the adhesive film, only the section of the adhesive film carrying out this holding function. The term “base surface” applies to that surface by which the sensor unit or the holding device of the state of the art would be glued to the interior side of the tire without an adhesive film according to the invention.
In a preferred embodiment, the length of the adhesive film measured in the circumferential direction of the vehicle tire is greater than the width of this vehicle tire, in which case, the adhesive film may naturally also still be greater than indicated by the figures. In an extreme case, the adhesive film may extend over the entire circumference of the interior side of the tire, particularly over the interior side of the running or tread surface of the tire. Particularly in the last-mentioned case, it is advantageous for the adhesive film to have an essentially diffusion-tight barrier layer, which prevents a creeping pressure loss in the tire, as known, for example, from German patent document 10 2004 020 076 A1.
In accordance with advantageous further developments of the present invention, the here so-called adhesive film can take over at least one additional function, besides the fixing of the tire pressure sensor unit on the interior side of the tire equipped with the sealing material. Thus, in addition to this sensor unit, an additional unit preferably used for the monitoring of the tire, or a unit obtaining electric energy or data from the movement of the tire may be provided on the adhesive film or be held on the interior side of the tire by the adhesive film. As examples of units used for the monitoring of the tire, moisture sensors, temperature sensors or a puncture sensor can be mentioned, in which case, a puncturing of the tire can also be determined, for example, by means of a moisture sensor. Piezo elements, for example, can be used as structures for generating energy, which piezo elements generate electric energy from deformations or vibrations; or other elements can be used which utilize thermal differences. Such elements may also be provided in the form of a layer on an adhesive film. Strain gauges can be used for the obtaining of data, for example, by way of the vertical tire forces. Finally, an antenna for the telemetric signal transmission to an electronic monitoring unit provided in the vehicle body may also be integrated in the adhesive film, or the adhesive film may carry such an antenna. In particular, if, as mentioned above, several electric elements are provided in the tire or on the adhesive film, which are electrically connected with one another, such an electric connection may be provided, for example, between the sensor unit or an electric terminal area provided for the latter and a further unit or a further element. In this case, the adhesive film may, for example, consist of a flexible strip conductor film, such as a copper-coated polyimide film, coated with an adhesive for the connection with the sealing material.
The currently used tire pressure sensor units are integrated in rigid housings or are cast into a hard casting compound, which, under extreme marginal conditions, may, however, have the result that the interior tire surface may be damaged in the event of a heavy load on the tire, or that, when driving over an obstacle, the components are damaged that are provided in the sensor unit. Such an effect can be avoided when the sensor unit is quasi-floatingly disposed in a gel-type mass, which is basically known; compare, for example, International patent document WO2005/002887 A2.
In the present case, the adhesive film according to the invention may now be constructed for accommodating such a gel-type mass. The adhesive film or a further film-type structure fixed thereto therefore forms a receptacle for this electrically non-conductive gel, in which the electric-electronic components of the sensor unit are disposed, in which case, as a function of properties of the gel and/or of the further development of the pressure sensor of the sensor unit, a connection between the pressure sensor of the sensor unit and the interior of the tire may be or should be provided, which connection is sealed off with respect to an exiting of gel, in order to permit a measuring of pressure. As a result of such an arrangement in an electrically non-conductive gel, the components of the sensor unit are advantageously protected from an effect of moisture.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.